Micro electro-mechanical devices are becoming increasingly popular and normally involve the creation of devices on the μm (micron) scale utilising semi-conductor fabrication techniques. For a recent review on micro-mechanical devices, reference is made to the article “The Broad Sweep of Integrated Micro Systems” by S. Tom Picraux and Paul J. McWhorter published December 1998 in IEEE Spectrum at pages 24 to 33.
One form of micro electro-mechanical devices in popular use are ink jet printing devices in which ink is ejected from an ink ejection nozzle chamber. Many forms of ink jet devices are known.
Many different techniques on ink jet printing and associated devices have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).
Recently, a new form of ink jet printing has been developed by the present applicant, which is referred to as Micro Electro Mechanical Inkjet (MEMJET) technology. In one form of the MEMJET technology, ink is ejected from an ink ejection nozzle chamber utilising an electro mechanical actuator connected to a paddle or plunger which moves towards the ejection nozzle of the chamber for ejection of drops of ink from the ejection nozzle chamber.
In previous designs of actuator a lower arm is deposited as a generally planar single layer, a sacrificial spacing layer is formed and then an upper arm is deposited as a generally planar layer.
A major portion of the cost of a manufactured wing semiconductor manufacturing techniques device depends on the number of separate layers required to be deposited during fabrication. Reducing the number of separate layers that need to be deposited reduces the cost of the device.
The efficiency of the thermal actuator is roughly inversely proportional to the mass of the actuator material. The actuator arms need to have a certain stiffness. If the stiffness of the arms can be maintained whilst decreasing mass, the efficiency of the actuator can be improved.
The present invention, in preferred forms, aims to address either or both of these issues.